The use of tertiary amines and certain organotin compounds, separately or in combination, as catalysts in the production of polyurethanes and polyisocyanurates is well known in the art. Among the more commonly employed tertiary amine catalysts are included triethylenediamine, N,N-dimethylcyclohexylamine, dimethylethanol amine, tetramethylbutane diamine, and N-methyl- and N-ethylmorpholine.